1. Field of the Invention
This invention relates to a process for producing a water-in-oil (w/o) polymer emulsion. More particularly, it relates to a process for production of a polymer emulsion useful in waste-water treatment or paper-making operations.
2. Description of the Prior Art
Generally, water-soluble or hydrophilic polymers have been industrially available in forms of powders, pastes, or w/o emulsions. Among these, w/o emulsions have recently been regarded as remarkable owing to their easy dispersibility or rapid dissolution in water as well as their ease of continuous or series dissolution.
However, in conventional w/o polymer emulsions, most of the time an accelerating agent for inversion of phase (a so-called activator) must be used to dissolve the polymer in the emulsions homogeneously into water and also these emulsions have the drawbacks of difficulties in passage through narrow pipes due to poor fluidity and of instability are the course of time.
In these respects, if a w/o polymer emulsion were produced from the ethylenically unsaturated monomer having the general formula (I) of the invention, or from a monomer mixture containing this monomer, there would remain the same problems so long as the polymerization procedures of the prior art were followed. For instance, the process of production of a w/o emulsion using a conventional w/o surfactant with a low HLB value has been disclosed in the specification of Japanese Patent Publication No. 10644,1959; however, according to that process, the produced emulsion has poor fluidity with a rather high apparent viscosity and poor stability. In order to dissolve the polymer of the emulsion in water, the addition of an accelerating agent for inversion of phase is always necessary. Furthermore, in laid open Japanese Patent Publication No. 72982/1975 is described another process for production of a w/o emulsion, wherein a surfactant having an HLB value of at least 7 is used in an mount of 20 percent by weight or more based on the oil phase. According to the process, the produced emulsion has a poor fluidity and a high apparent viscosity. Therefore, there have always been problems, including required vigorous agitation during production and difficult conduction of the product through a narrow pipe.